Reverse osmosis-ion exchange water purification



Sept. 1, 1970 B. H. KRYZER 3,525,320

REVERSE QSMOSIS-ION EXCHANGE WATER PURIFICATION Filed Jan. 18, 1968////a/w4m United States Patent O 3,526,320 REVERSE OSMOSIS-ION EXCHANGEWATER PURIFICATION Benjamin H. Kryzer, St. Paul, Minn., assignor, bymesne assignments, to Union Tank Car Company, Chicago, 111., acorporation of Delaware Filed Jan. 18, 1968, Ser. No. 698,783 Int. Cl.B01d 31/00 US. Cl. 210-254 5 Claims ABSTRACT OF THE DISCLOSURE Water ispurified by conducting it through a semipermeable membrane to removeimpurities by reverse osmosis, storing the Water, and selectivelyutilizing the stored water or conducting it through an ion exchangeresin module. Water that has passed through the ion exchange resin willbe more pure than that which has passed only through the semi-permeablemembrane. The invention also provides apparatus including suitablereverse osmosis means, a water storage tank, and ion ex change resinmeans, connected in series by suitable pipe means. Means are providedfor withdrawing water directly from the storage tank, optionallybypassing the ion exchange resin, and avoiding unnecessary exhaustion.

The present invention relates to improvements in the art of purifyingwater, and more specifically to an improved method and apparatus forremoving impurities from water by reverse osmosis and ion exchange.

There is often a need, especially in the laboratory, for very purewater. On the other hand, in many applications the water need not beextremely pure, so long as the majority of the dissolved contaminantshave been removed. While reverseosmosis can remove the majority ofdissolved and undissolved contaminants from water, it is not thepreferred method for producing extremely pure water. The removal ofsubstantially all impurities from water by reverse osmosis would requirerelatively high pressures, while only a small portion of the water wouldbe passed through the membrane. It is therefore an uneconomicalprocedure. The use of ion exchange resins is best for producing suchextremely pure Water. However, ion exchange resins are expensive in thatthey must be replaced or regenerated when they become exhausted. Resinsare therefore somewhat impractical for overall laboratory use.

Generally the present invention provides a method for purifying waterwherein the water is conducted through a semi-permeable membrane toremove the majority of the dissolved and undissolved impurities byreverse osmosis. At least a portion of the water is then stored, whereit may be selectively Withdrawn for use or conducted through ionexchange resin in order to remove any remaining ionic impurities.

The present invention also provides apparatus for carrying out theaforementioned method, the apparatus including reverse osmosis meanshaving a water supply inlet, a hard water outlet, and a purified wateroutlet, along with ion exchange resin means including a water inlet, awater outlet, and ion exchange resin therebetween. Finally, theapparatus includes storage means having an inlet and an outlet, thestorage inlet communicating with the purified Water outlet of thereverse osmosis means, and the storage outlet communicating with thewater inlet of the ion exchange means. Preferably, the storage means arelocated above the water outlet of the ion exchange means in order topermit the water to be fed through the ion exchange means under theforce of gravity.

3,526,320 Patented Sept. 1, 1970 The invention, both as to itsorganization and method of operation, together with the objects andadvantages thereof, will be best understood from the following detaileddescription taken in conjunction with the drawing, which is an elevationview of a preferred embodiment of the present invention.

As previously mentioned, the method of the present invention comprisesconducting water through a semipermeable membrane to remove impuritiesby reverse osmosis. At least a portion of the water is stored after ithas passed through the membrane, and at least a portion of the storedwater is selectively conducted through ion exchange resin.

As is well known in the art, semi-permeable membranes suitable forreverse osmosis fall into several categories depending upon the type ofcontaminants that are to be removed. Membranes are available to retardthe passage of only relatively large, uncharged molecules, or to retardcations or anions. Although any type of membrane may be employed in thepresent invention, depending upon the impurities to be removed from thewater, it is preferred to employ a membrane that retards the passage ofanions and cations as well as dissolved and suspended nonionicimpurities as are found in ordinary tap water. The stored water, whichis relatively pure, can then be selected when highly purified water isnot required, avoiding the unnecessary exhaustion of the ion exchangeresin.

The stored water may also be conducted through the ion exchange resin,where it will be further purified. As is well known in the art, ionexchange resin may be obtained in either the softening type or thedemineralizing type. The softening type exchanges non-precipitateformingions such as sodium for the hardness ions, primarily as calcium andmagnesium. The demineralizing type of resins, which is clearly preferredin the present invention, exchanges hydrogen or hydroxide ions for thoseremoved from the water. These resins are available in strong and Weakacid hydrogen form as well as strong and weak base hydroxide form. Anyof the four may be utilized, depending upon the ions to be removed fromthe water and the desired pH of the treated water. In the preferredembodiment, both hydrogenand hydroxideform resins are employed, eithermixed or in series to remove both anionic and cationic impurities. Inthe most preferred embodiment, all four forms are used in series toproduce effluent water of nearly neutral pH.

Referring to the drawing, the preferred embodiment of the presentinvention comprises Water purification apparatus generally indicated byreference numeral 10. The apparatus shown is of a type suitable for achemical laboratory and includes a baseboard 12 which is suitable forwall mounting in a vertical position. Secured on a lower portion of thebaseboard 12 by brackets 13 is a reverse osmosis module 14 having a rawwater inlet opening 16, a purified water outlet 18, and a hard wateroutlet 20. The raw water inlet opening 16 communicates with a supplypipe 21. Attached to the side of the reverse osmosis module 14 by astrap 22 is a flow restrictor 24 communicating with the hard wateroutlet 20 by a pipe section 26. As is well known in the art, a flowrestrictor 24 is essential to provide sufficient pressure on the hardwater side of the membrane for the reverse osmosis process to takeplace.

Purified water from the reverse osmosis module 14 is conducted to awater storage tank 28 through a suitable pipe 30. As shown in thedrawing, the water storage tank 28 is secured to an upper portion of thebaseboard 12 by a mounting bracket 32. At the upper portion of thestorage tank 28 are a water inlet 34, an overflow outlet 36, and an airvent 38. Partially purified water from the reverse osmosis module 14 isconducted to the water 3 storage tank 28 through the pipe 30,communicating with the water inlet 34. Air displaced as the storage tankis filled or emptied is vented through the air vent 38.

The reverse osmosis module is preferably run continuously, so that afterthe tank 28 is filled, and provided there is no demand for the Watercontained therein, the excess will flow out of the overflow outlet 36through a pipe 40 to a drain pipe 42 communicating with drain means (notshown). Preferably, an air gap 44 is provided between the overflowoutlet 36 and the drain pipe 42 in order to prevent the possibility ofbacksiphoning from the drain pipe 42 into the stroage tank 28. As shownin the drawing, the hard water outlet pipe 46 is connected to the flowrestrictor 24 on the side of the reverse osmosis module 14 to conducthard water from the module 14 to the pipe 40 communicating with theoverflow outlet 36. The hard water is thus disposed of through the drainpipe 42 along with the overflow water from the storage tank 28.

Communicating with the storage tank 28 at a point near the bottomthereof is a semi-purified water outlet pipe 48 including faucet orvalve means 50 at the bottom end thereof. It can be seen that liquidwithdrawn from the valve means 50 will have passed through the reverseosmosis module 14, and will therefore have most of the impuritiesremoved.

An ion exchange resin module 52 is mounted on the baseboard 12 at apoint below the Water storage tank 28 for reasons that will hereinafterappear. Water from the semi-purified water outlet pipe 48 is conductedto the bottom of the ion exchange resin module 52 through a connectingpipe 54. The ion exchange resin module 52 is filled with ion exchangeresin, preferably of the hydrogen and hydroxide form, which removesionic impurities from the water. The hydrogenand hydroxide-form resinsmay be present either in a mixed bed or in separate beds, although thelatter are preferred. A particularly preferred construction includesfour beds in series, and in the following order: strong cationicexchange resin, strong anionic exchange resin, weak cationic exchangeresin, and weak anionic exchange resin. Such a sequence providespurified water of nearly neural pH.

It is also often suitable to include a dye in the ion exchange resinwhich changes color as the resin is eX haused. In the embodiment shown,the ion exchange resin module 52 is mounted on the baseboard 12 by snapbrackets 56 which allow the simple removal of exhausted ion exchangeresin modules and their replacement with fresh ones.

The connecting pipe 54 communicates with the inlet opening 58 on thebottom of the ion exchange resin module 52. Under the pressure of thehydrostatic head of water maintained in the storage tank 28, waterpasses upwardly through the ion exchange resin module 52 to a wateroutlet opening 60, and into a fully purified water outlet pipe 62.Faucet or valve means 64 communicate with the bottom end of the purifiedwater outlet pipe 62. It will be seen that by maintaining the valvemeans 64 on the fully purified water outlet pipe 62 below the level ofthe water storage tank 28, water may easily be withdrawn through the ionexchange resin module 52 under the force of gravity alone, thusproviding a relatively simple apparatus.

In operation, the raw water inlet pipe 16 is connected to a suitablewater source, and water is delivered to the reverse osmosis module 14.It is essential that this water be supplied at a pressure sulficient forthe reverse osmosis process to take place. If ordinary line pressure isinsutficient, a pump (not shown) may be employed to boost the pressure.Hard water, which will be enriched in impurities, passes out the hardwater outlet 20, through the flow restrictor 24 and the hard wateroutlet pipe 46 to the drain pipe 42 where it is disposed of. Purifiedwater from the reverse osmosis module 14 passes out the purified wateroutlet 18 through the pipe 30' to the water inlet 34 of the waterstorage tank 28. The tank 28 fills, any excess passing to the drain pipe42 through the overflow outlet 36.

If water of a semi-purified nature is required, it may be withdrawn fromthe water storage tank 28 opening the valve means 50 at thelower end ofthe semi-purified water outlet pipe 48. On the other hand, if water of avery pureinature is required it is withdrawn from the apparatus 10 byopening the valve means 64 at the bottom of the fully purified wateroutlet pipe 62. Because the water storage tank 28 is located above theion exchange resin module 52, water will pass through the module 52under the force of gravity.

While the embodiments described hereinare at present considered to bepreferred, it will be understood that various modifications andimprovements may be made therein and it is intended to cover in theappended claims all such modifications and improvements as fall withinthe true spirit and scope of the invention.

I claim:

1. Laboratory water purification apparatus comprising: a baseboardadapted for vertical mounting; a reverse osmosis module mounted on alower portion of said baseboard, said reverse osmosis module having awater inlet, a hard water outlet communicating with a drain, and apurified water outlet; a water storage tank mounted on an upper portionof said baseboard, said-water storage tank indicating a water storageinlet and outlet, an overflow outlet, and an air vent, said waterstorage inlet communicating with said purified water outlet of saidreverse osmosis module, and said overflow outlet communicating withdrain means; an ion exchange resin module mounted on a lower portion ofsaid baseboard, said ion exchange resin module including a water inlet,a water outlet, and hydrogenand hydroxide-form ion exchange resinbetween said inlet and outlet, said water inlet of said ion exchangeresin module communicating with said water storage outlet; asemi-purified water outlet between said water storage outlet and saidwater inlet of said ion exchange resin module, said semi-purified wateroutlet including a valve operable to withdraw water from said waterstorage tank; and a fully purified water outlet communicating with saidwater outlet of said ion exchange resin module, said fully purifiedwater outlet including a valve operable to withdraw water from saidstorage tank through said ion exchange resin module.

2. Laboratory water purification apparatus comprising: a reverse osmosismodule having a water inlet, a hard water outlet communicating with adrain, and a purified water outlet; 21 water storage tank including awater storage inlet and outlet, and an air vent, said water storageinlet communicating with said purified water outlet of said reverseosmosis module, an ion exchange resin module including a water inlet, awater outlet, and hydrogen and hydroxide-form ion exchange resin betweensaid inlet and outlet, said water inlet of said ion exchange resinmodule communicating with said water storage outlet; a semi-purifiedwater outlet between said water storage out let and said water inlet ofsaid ion exchange resin module, said semi-purified water outletincluding a valve operable to withdraw water from said water storagetank; and a fully purified water outlet communicating with said wateroutlet of said ion exchange resin module, said fully purified wateroutlet including a valve operable to withdraw water from said storagetank through said ion exchange resin module.

3. Laboratory water purification apparatus comprising: a reverse osmosismodule having a water inlet, a hard water outlet communicating with adrain, and a purified water outlet; a water storage tank including awater storage inlet and outlet, an overflow outlet, and an air vent,said water storage inlet communicating with said purified water outletof said reverse osmosis module, and said overflow outlet communicatingwith drain means, an ion exchange resin module positioned below saidwater storage tank, including a water inlet, a Water outlet, andhydrogen and hydroxide-form ion exchange resin between said inlet andoutlet, said water inlet of said ion exchange resin module communicatingwith said water storage outlet; a semi-purified water outlet betweensaid water storage outlet and said water inlet of said ion exchangeresin module, said semi-purified water outlet including a valve operableto withdraw water from said water storage tank; and a fullypurified-water outlet communicating with said water outlet of said ionexchange resin module, said fully purified water outlet including avalve operable to withdraw water from said storage tank through said ionexchange resin module.

4. Laboratory water purification apparatus comprising: a baseboardadapted for vertical mounting; a reverse osmosis module mounted on saidbaseboard, said reverse osmosis module having a water inlet, a hardwater outlet communicating with a drain, and a purified water outlet; awater storage tank mounted on said baseboard, said water storage tankincluding a water storage inlet and outlet, and an overflow outlet, saidWater storage inlet com municating with said purified water outlet ofsaid reverse osmosis module, and said overflow outlet communicating withdrain means, an ion exchange resin module mounted on said baseboard,said ion exchange resin module including a water inlet, a water outlet,and hydrogen and hydroxide-form ion exchange resin between said inletand outlet, said water inlet of said ion exchange resin modulecommunicating with said water storage outlet; a semipurified wateroutlet between said water storage outlet and said water inlet of saidion exchange resin module, and semi-purified water outlet including avalve operable to withdraw water from said water storage tank; and afully purified water outlet communicating with said water outlet of saidion exchange resin module, said fully purified water outlet including avalve operable to withdraw water from sad storage tank through said ionexchange resin module.

5. Laboratory water purification apparatus comprising: a reverse osmosismodule having a water inlet, a hard water outlet communicating with adrain, and a purified water outlet; a water storage tank including awater storage inlet and outlet, an overflow outlet, said water storageinlet communicating with said purified water outlet of said reverseosmosis module, and said overflow outlet communicating with drain means,an ion exchange resin module including a water inlet, a water outlet,and hydrogen and hydroxide-form ion exchange resin between said inletand outlet, said water inlet of said ion exchange resin modulecommunicating with said water storage outlet; a semi-purified wateroutlet between said water storage outlet and said water inlet of saidion exchange resin module, said semi-purified water outlet including avalve operable to withdraw water from said water storage tank; and afully purified water outlet communicating with said water outlet of saidion exchange resin module, said fully purified water outlet including avalve operable to withdraw water from said storage tank through said ionexchange resin module.

References Cited UNITED STATES PATENTS 683,061 9/ 1901 Nordtmeyer210-249 X 1,825,631 9/1931 Horvath 210-321 X 3,390,773 7/1968 Merten 21032l X 3,397,785 8/1968 Jarvis et al. 210125 OTHER REFERENCES ReverseOsmosis, a publication of General Dynamics, General Atomics Division,May 1967, 6 pages.

REUBEN FRIEDMAN, Primary Examiner F. A. SPEAR, 111., Assistant ExaminerUS. Cl. X.R. 210-257, 262, 321

